Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997) / Chapter Skim
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4 Calcium
4 Calcium
Pages 71-145
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From page 71... ...
, and bone mineral is almost 40 percent of the weight of bone. Bone is a dynamic tissue that is constantly unclergoing osteoclastic bone resorption and osteoblastic bone formation.
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From page 72... ...
Passive diffusion becomes more important at high calcium intakes (Irelanci and Forcitran, 1973~. It has long been recognized that fractional calcium absorption varies inversely with clietary calcium intake (Irelanci and Forcitran, 1973; Maim, 1958; Spencer et al., 1969)
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From page 73... ...
found that African Americans haci similar calcium absorption efficiency but lower urinary calcium excretion than Caucasians. Abrams and colleagues (1996a)
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From page 74... ...
High tinily calcium intakes (over 1,000 mg t25 mmol]
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From page 75... ...
This linkage holds at moderate and high calcium intakes, but some dissociation occurs at low calcium intakes (Dawson-Hughes et al., 1996) , probably because low calcium intakes induce higher PTH levels, and PTH promotes the reabsorption of filtered calcium in the distal renal tubule.
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From page 76... ...
and has been associated with increaseci hip fracture risk in women (Kiel et al., 1990~. The association of caffeine consumption with accelerated bone loss has been limited to postmenopausal women with low calcium intakes (Harris and Dawson-Hughes,1994~.
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From page 77... ...
In a different study of women with low usual calcium intakes, supplementation with 500 mg (12.5 mmol) /ciay of calcium haci no significant impact on bone loss from the spine or other sites in early postmenopausal women, but it significantly recluceci bone loss in women more than ~ years beyond menopause (Dawson-Hughes et al., 1990~.
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From page 78... ...
Early postmenopausal Aloia et al., 1994b 70 500 1,700 S or N P no Dawson-Hughes et al., 1990 67 <400 500 P P no Prince et al., l991e 80 800 1,000 P P no Riis et al., 1987 25 ~1,000 2,000 P P yes Late postmenopausal Dawson-Hughes et al., 1990 169 <400 500 (CCM)
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From page 79... ...
fAn 18-month study in 82 women and 11 men. g Supplement tablets and milk powder significantly reduced bone loss at the trochanter.
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From page 80... ...
On balance, lacto-ovovegetarians and omnivores appear to have fairly similar clietary calcium intakes (Marsh et al., 1980; Peclersen et al., 1991; Reed et al., 1994) and, on the same intakes, to have similar amounts of urinary calcium excretion (Lloyd et al., 1991; Tesar et al., 1992)
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From page 81... ...
, showed that mean daily calcium intake, based on an adjusted 24-hour recall which allows for varying degrees of departure from normality and recognizes the measurement error associated with one-day dietary intakes (Nusser et al., 1996) , was about 25 percent higher in males than in females aced 9 years and older in ~ ~ ~ , the United States (925 vs.
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From page 82... ...
/day for women. Data from 11,643 adults who participated in the 1992 NHIS show that calcium intakes are higher for both men and women who take clietary supplements (of any kind)
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From page 83... ...
Thus, although PTH maintains a normal circulating calcium concentration cluring calcium deprivation, it clods so at the expense of skeletal mass. Dietary Calcium and Osteoporosis Osteoporosis is characterized by recluceci bone mass, increased bone fragility, and increased risk of fracture (WHO, 1994~.
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From page 84... ...
Calcium Intake and Fracture Risk Ideally, the optimal calcium intake for skeletal health would be clefineci as that which leacis to the fewest osteoporotic fractures later in life. Attaining this information would require prospective cletermination of the influence of different increments in calcium intake on fracture rates in young and older subjects with a wicle range of usual calcium intakes.
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From page 85... ...
Bone Mass Measurements Bone mineral content (BMC) is the amount of mineral at a particular skeletal site such as the femoral neck, lumbar spine, or total body.
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From page 86... ...
. This technique has already revealed that the patterns and timing of acquisition of peak bone mass vary by skeletal site, and that bone loss from trabecular- and cortical-rich sites occurs at different rates in women at menopause (see Table 41~.
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From page 87... ...
In this report, classic metabolic studies of calcium balance were used to obtain ciata on the relationship between calcium intakes and retention from which a non-linear regression model was clevelopeci; and from this was cleriveci an intake of calcium which would be adequate to attain a precletermineci desirable calcium retention. This approach is a further refinement of an earlier approach suggesteci to determine the point at which aciclitional calcium clods not significantly increase calcium retention, called the plateau intake (Matkovic and Heaney, 1992; Spencer et al., 1984)
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From page 88... ...
By selecting studies conclucteci on such subjects, it obviates the concern about whether the bone remodeling transient might introduce bias in the calcium retentions observed. Such selection was not possible in studies in children where they have been ranclomizeci to one of two calcium intakes.
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From page 89... ...
. The major limitation of the ciata available is that bone mineral accretion cluring growth has not been stuclieci over a wicle range of calcium intakes.
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From page 90... ...
[imitations of the Evidence In reviewing the scientific literature to provide the best estimate of calcium requirements for each stage of the lifespan, needed data were not always available. In most instances, calcium intake ciata could not be matched with the outcome criteria of both calcium retention and bone mass in the same subjects.
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From page 91... ...
uncertainties in the methods inherent in and the precise nutritional significance of values obtained from the balance studies that form the basis of the desirable retention model; (2) the lack of concordance between observational and experimental ciata (mean calcium intakes in the United States and Canada are much lower than are the experimentally cleriveci values preclicteci to be required to achieve a desirable level of calcium retention)
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From page 92... ...
Mean absorption was 61 + 22 percent of intake when approximately 80 percent of the dietary calcium was from human milk. There was no significant relationship between calcium from solici foocis and the fractional calcium absorption from human milk.
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From page 93... ...
/day will result in retention of sufficient amounts of calcium to meet growth needs. For infants in the first 4 months of life, balance studies suggest that 40 to 70 percent of the daily calcium intake is retained by the human milk-fed infant (Fomon and Nelson, 1993; Widdowson, 1965)
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From page 94... ...
Although limited data are available for typical calcium intakes from foocis by human milk-feci older infants, mean calcium intakes from solici foocis are 140 mg (3.5 mmol) /ciay for formula-feci infants (Abrams et al., 1997a; Specker et al., 1997~.
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From page 95... ...
This fincling is supported by a study in clogs suggesting that in forming stable bone, low calcium intakes early in life might be preferred to greater intakes (Gershoff et al., 1958~. These finclings neeci to be replicated to determine whether this effect is relevant to full-term infants.
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From page 96... ...
In 2- to 8-year-old children, mean calcium intakes (+ SD) of 821 + 63 mg (20.5 + 1.5 mmol)
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From page 97... ...
Intervention trials in which children were ranclomizeci to clifferent calcium intakes have resulted in short-term changes in BMC. In one of the few intervention trials conclucteci in young children, 22 prepubertal identical twin pairs averaging 7 years of age were ranclomizeci to receive either calcium supplements or placebo Johnston et al., 1992~.
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From page 98... ...
In a follow-up study for another 18 months, the benefits of calcium supplementation clisappeareci after the supplements were withdrawn (Lee et al., 1996~. In a similar study, greater increases in lumbar spine BMC were seen in 7-yearolci children from Hong Kong with average calcium intakes of 570 mg (14.3 mmol)
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From page 99... ...
Ages 9 through I3 and I4 through IS Years Sexual Maturity From 9 through 18 years of age, calcium retention increases to a peak and then declines. The peak calcium accretion rate typically occurs at mean age 13 years for girls and 14.5 years for boys (Martin et al., 1997~.
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From page 100... ...
in girls. One limitation of these ciata is that they do not provide information as to whether peak bone mineral accretion would be greater at higher calcium intakes than that consumed by the children stuclieci; the mean intake for boys was 1,045 mg (26 mmol)
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From page 101... ...
The measurements were macle over the last 2 weeks of a 3-week balance study in girls consuming calcium intakes of 823 to 2,164 mg (20.6 to 54.1 mmol) /clay.
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From page 102... ...
Further research is required to determine the longterm effects of higher calcium intakes cluring adolescence and the specific effect of calcium intake on bone mocleling and achievement of genetically programmed peak bone mass. Factorial Approach.
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From page 104... ...
, whereas others have found no such association (Grimston et al., 1992; Katzman et al., 1991; Kroger et al., 1992, 1993~. The studies showing the positive association tended to include a significant proportion of study subjects with low calcium intakes.
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From page 105... ...
As it appears now, and pencling further research in this area, higher calcium intakes likely neeci to be maintaineci throughout growth in order to produce a higher peak bone mass. Al Summary: Ages 9 through I3 and I4 through IS Years The three major lines of evidence for calcium neecis in this age group the factorial approach, calcium retention to meet peak bone mineral accretion, and clinical trials in which bone mineral content was measured in response to variable calcium intakesprovicle estimates of calcium intake in the range of 1,100 to 1,600 mg (27.5 to 40 mmol)
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From page 106... ...
Using single measures of BMC by DXA on 247 females aged 11 to 32 years, 92 percent of the total body bone mass observed was present by age 17.9 years and 99 percent by age 26.2 years (Teegarden et al., 1995~. In a crosssectional study of 265 Caucasian females, only a 4 percent additional increase in total skeletal mass from age 18 to 50 years was reported (Matkovic et al., 1994~.
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From page 107... ...
A desirable level of calcium retention (the level of positive calcium balances for the 19- to 30-year age group was set to the reported calcium accrehon derived trom studies ot bone mineral accretion during the third decade (Peacock, 1991~. The limitation of these data is that they were derived from metacarpal morphometry data (Garn, 1972)
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From page 108... ...
than the clesirable calcium retention approach (see above)
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From page 109... ...
For this age group, as for the others, balance studies were examined to identify the intake associated with a clesirable calcium retention the plateau intake, that at which there is no net loss of calcium. Two balance studies are available that examineci estrogen-replete women on their usual calcium intakes (Heaney et al., 1978; Ohlson et al., 1952~.
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From page 110... ...
However, the intake associated with a desirable retention so that no net loss will occur cannot be iclentifieci without aciclitional balance studies in women with calcium intakes greater than 1,000 mg (25 mmol) /ciay.
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From page 111... ...
The distribution of intakes in the 181 balance studies were: 111 balance studies in subjects with tinily calcium intakes below 1,200 mg (30 mmol) , 22 at approximately 1,200 ma, and 48 at intakes above 1,200 ma.
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From page 112... ...
Women have been more widely stuclieci regarciing calcium retention because they are particularly prone to osteoporosis. Several balance studies are reported in postmenopausal women with mean calcium intakes uncler 1,000 mg (25 mmol)
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From page 113... ...
/ clay have less calcium loss when they increase their calcium intake. Only two balance studies in postmenopausal women with average usual calcium intakes higher than 1,000 mg (25 mmol)
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From page 114... ...
/ciay was cleriveci from the calcium retention model using balance studies in men, there were no data for calcium intakes between 800 and 1,200 mg (20 and 30 mmol) /ciay.
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From page 115... ...
Ages > 70 Years Indicators Used to Set the Al Calcium Retention. Few men over age 70 have participated in balance studies.
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From page 116... ...
Two other studies have assessed the effect of calcium alone on fracture rates (Chevalley et al., 1994; Recker et al.,1996~. Among women with low usual ciaily calcium intakes (mean 450 mg t11.3 mmol]
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From page 117... ...
Thus, nearly all women ages > 70 years are consuming less calcium than the AI. Summary of Approaches Used for Adolescents and Adults Desirable rates of calcium retention, cletermineci from balance studies, factorial estimates of requirements, and limited ciata on BMD and BMC changes, have been used as the primary indicators of adequacy (Table 4-~.
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From page 118... ...
. c The calcium retention model was based on balance studies from which the absolute intake and retention of individual subjects was modeled using non-linear regression analysis (Jackman et al., 1997)
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From page 119... ...
e These estimates were not derived from statistical analysis of calcium intake and retention data to determine desirable calcium intakes due to limitations in the range of calcium intakes that had been studied.
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From page 120... ...
Calcium retention exceecleci the clemanci for fetal growth. A possible explanation for the increased calcium retention in these balance studies is that the mothers were still accreting bone regardless of their pregnancy state; the ages of the mothers ranged from 1 ~ to 28 years.
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From page 121... ...
It was not stated in these studies whether calcium intake moclifieci the relationship between the number of pregnancies and BMD or fracture risk. Al Summary for Pregnancy Taken together, the available ciata on bone mineral mass cluring pregnancy and the lack of correlation between the number of pregnancies and BMD or fracture risk provide sufficient information to support the concept that the maternal skeleton is not used as a reserve for fetal calcium neecis.
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From page 122... ...
2D leacling to enhanced calcium absorption. Although investigators have reported high serum 1,25 (OH)
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From page 123... ...
A ranclomizeci trial of calcium supplementation at approximately 1,000 mg (25 mmol) /day for ~ days in lactating women accustomed to low calcium intakes (approximately 300 mg t7.5 mmol]
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From page 126... ...
The changes in bone mass that occur at this time are likely to be more related to the effects of lack of estrogen than to the increased demand of calcium for milk production. Therefore, it clods not appear that clietary calcium intakes above that recommended for nonlactating women minimizes the bone loss observeci cluring lactation, nor clods it augment the bone gain cluring weaning.
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From page 127... ...
A longitudinal prospective study of over 9,000 women over the age of 65 found that the risk of hip fracture was not associated with the number of children who were breast-feci (Cummings et al., 1995~. Although most studies have found no increase in fracture risk with a history oflactation,Kreigerancicoworkers (1982)
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From page 128... ...
128 V, U Vet to ~4 to 55- = c4 U o G\r o o o · ~ V)
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From page 129... ...
129 at, in, ~ ~ ~ Go At, ~ ~ ~ ~ o o ~ ~ ~ ~ ~ ~ I I ~ ~ I o I o I o o o I o I o ~ o ~ ~ G\r o G\r ~ G\r ~ ~ G\r ~ G\r G\r ~ G\r ~ ~ ~ ~rim ~ rim ~ rim ~ rim ~ rim ~ rim V)
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From page 132... ...
Therefore, it clods not appear, from the data available at this time, that closely spaced pregnancies least to a lower bone mass in these women than in women with pregnancies less closely spaced. Feeding More Than One Infant.
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From page 133... ...
. Although the results of these studies are intriguing, several concerns about the finclings have been expressed, including not fincling bone loss in the adult women, a higher rate of bone loss than that seen in any pathological conclition, and bone mass mea
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From page 134... ...
As a result, disturbances of calcium metabolism give rise to a wicle variety of adverse reactions. Disturbances of calcium metabolism, particularly those that are characterizeci by changes in extracellular ionized calcium concentration, can cause damage in the function and structure of many organs and systems.
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From page 135... ...
In aciclition to being associated with increased calcium intakes, nephrolithiasis appears to be associated with higher intakes of oxalate, protein, and vegetable fiber (Massey et al., 1993)
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From page 136... ...
These reports clescribeci what appears to be the same syndrome at supplemental calcium intakes of 1.5 to 16.5 g (37.5 to 412.5 mmol) /ciay for 2 clays to 30 years.
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From page 137... ...
. Similarly, except for a single report of negative zinc balance in the presence of calcium supplementation (Wooci and Zheng, 1990)
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From page 138... ...
/ciay can be iclentifieci for adults (Table 4-10~. A review of these reports revealed calcium intakes from supplements (anci in some cases from clietary sources as well)
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From page 139... ...
CALCIUM TABLE 4-10 Case Reports of Milk Alkali Syndrome (single dose/day) a 139 Ca Intake Mitigating Studies (g/d)
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From page 140... ...
, and (3) concern for the potential increased risk of mineral clepletion in vulnerable populations clue to the interference of calcium on mineral bioavailability, especially iron and zinc.
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From page 141... ...
Although calcium supplementation in children may appear to pose minimal risk of MAS or hyperabsorptive hypercalciuria, risk of depletion of other minerals associated with high calcium intakes may be greater. With high calcium intake, small children may be especially susceptible to deficiency of iron and zinc (Golden and Golden, 1981; Schlesinger et al., 1992; Simmer et al., 1988)
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From page 142... ...
, absorption of calcium, except when associated with meals, is likely to be somewhat impaired, which would protect these individuals from the adverse effects of high calcium intakes. Furthermore.
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From page 143... ...
. Calcium supplements were used by less than 8 percent of young children, 14 percent of men, and 25 percent of women in the United States (Moss et al., 1989~.
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From page 144... ...
Good surrogate markers of osteopenia could be used in epiclemiological studies. · Assessment of the effect of ethnicity and osteoporosis phenotype on the relationship between clietary calcium, desirable calcium retention, bone metabolism, and bone mineral content.
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From page 145... ...
CALCIUM 145 · More carefully controlled studies are neecleci to determine the strength of the causal association between calcium intake vis-a-vis the intake of other nutrients and kidney stones in healthy inclivicluals. · Because of their potential to increase the risk of mineral clepletion in vulnerable populations, calcium-mineral interactions should be the subject of aciclitional studies.
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